Headwinds on a Flight

[Butts]

Not being technically minded I always dread hearing the above words from the pilot as it usually means a delay.

Can an aeroplane safely just increase the power and maintain the same speed without any danger. I know this would result in burning more fuel but just curious if it is feasible.

 

[table38]

I'd say yes, because it's "air speed" verses "land speed". Perhaps counter-intuitively planes usually land and take-off into the wind because it increases the air speed and therefore the lift.

(Actually I suppose if you think about it, a plane trying to land at 80mph with an 80mph tail-wind wouldn't have any lift at all!)

However once at crusing altitude, you will need more fuel to do the same "land distance" against a head-wind.

Many moons ago I was involved in a project for ACNZ to plot wind speeds at different heights, as the fuel savings for a tail-wind as against a head-wind were significant.

Actually it was all explained here in the Radio 4 Series "Cabin Pressure"

DOUGLAS: Arthur, you were asking why the air over the wing has to keep up with the air underneath..
ARTHUR: Oh, yes, do you know?
DOUGLAS: Indeed, I do. Attend. The air is not passing over the wing. The wing is passing through the air. So the curved upper side stretches the air forced over it apart, reducing pressure, producing lift. The lift pushes up. The weight pushes down. So as long as the lift is more than the weight, up we go and that, my friend, is how an aeroplane flies.
ARTHUR: Got it! Right. Yes. Cracking. I completely get it now.
DOUGLAS: Good. You see, is that quite easy to grasp when it's explained properly by someone who understands..
ARTHUR: So that's why planes can't fly upside and down?
DOUGLAS: Uh..Yes, they can.
ARTHUR: Can they?
DOUGLAS: Well, of course they can. Haven't you seen the Red Arrows?
ARTHUR: But doesn't that mean the curved side of the wing is on the bottom? So the lift is pushing down as well as the weight. How does that work?
MARTIN: Yes, Douglas. How does that work?
DOUGLAS: Well, Arthur, there's a very simple explanation. But just to finish what we were saying, Martin, I think it's entirely up to you whether you let the cat in the hold freezed to death.
ARTHUR: What?!
MARTIN: Douglas!
ARTHUR: Skipper!
DOUGLAS: No one wants to hear the explanation. What a shame!

 

[Old Timer]

There are constant winds at the level at which long haul commercial airliners operate, the best know being the Jet Stream.

A headwind is favourable to an aircraft in most circumstances since it allows the aircraft to take off and climb faster however in flight the opposite is true because the plane then requires more fuel to fly into the headwind.

The Jest Stream moves from the west towards the east and when it is the tail wind aircraft can gain a considerable amount of time as in effect they are being propelled forward by the wind.

Part of the pre-ops planning is the calculation of fuel and this involves the prevailing wind speed and strength. The aircraft however will always have enough fuel to circle its destination with an allowance to fly to an alternative and stack there for 20 minutes, with a 10% additional allowance on top. This is why on some long haul flights the a/c will not always be fully loaded with passengers.

The flight deck crew will also have various alternative airports en route that they can head to in the event of any fuel issues although running out of fuel is a rare event indeed.


Winds in the upper atmosphere were unknown until the night of 30/31st March 1944 when a raid to Nuremburg went horribly wrong when the bombers got caught up in the lower edges of the Jet Stream with the resul that they arrived early on target and had to wait for the Pathfinders to arrive to mark the target.

That raid was the most costliest ever for the RAF with 106 aircraft lost, 96 of them shot down by night fighters or flak.

 

[Butts]

I know what you mean about the fuel regulations.

I once flew from Santiago to Paris and the aircraft actually had to land at another airport in France and refuel before carrying onto Paris.

The last thing you want after a 14 or 16 hour flight - so close yet so far

 

[Peter Mugridge]

Not being technically minded I always dread hearing the above words from the pilot as it usually means a delay.

Can an aeroplane safely just increase the power and maintain the same speed without any danger. I know this would result in burning more fuel but just curious if it is feasible.

You need to maintain the air speed - ignoring fuel consumption increases, if you put on more power to keep the land speed the same you run the risk of exceeding the aircraft's safe airspeed limit.

In any case it all averages out in the end - you'd have a tail wind if you were going in the other direction, with a shorter flying time as a result.

 

[Butts]

You need to maintain the air speed - ignoring fuel consumption increases, if you put on more power to keep the land speed the same you run the risk of exceeding the aircraft's safe airspeed limit.

In any case it all averages out in the end - you'd have a tail wind if you were going in the other direction, with a shorter flying time as a result.

True but when your "desparate for a burn" the last thing you want to hear is a delay

 

[Old Timer]

I know what you mean about the fuel regulations.

I once flew from Santiago to Paris and the aircraft actually had to land at another airport in France and refuel before carrying onto Paris.

The last thing you want after a 14 or 16 hour flight - so close yet so far

Air France by any slim chance ??

 

[Butts]

Air France by any slim chance ??

How did you guess - are they in the habit of flying "on fumes"

 

[WestCoast]

How did you guess - are they in the habit of flying "on fumes"

I don't think so, although I think they have the most blemished safety record of the national European airlines, but they are still very, very safe.

 

[Butts]

I don't think so, although I think they have the most blemished safety record of the national European airlines, but they are still very, very safe.

Yes I flew just after that one went down just off the coast of Brazil

Good things: Edinburgh - Paris opens up the whole network

Smoking Area at CDG in the waiting area for flights - post security.

Decent Cognac even in peasant class - no cigar though

 

[WestCoast]

Smoking Area at CDG in the waiting area for flights - post security.

Decent Cognac even in peasant class - no cigar though

The most "interesting" flight I've ever had was on a Cubana de Aviación Ilyushin Il-96 (a Russian relic all the way from Gatwick to Havana!) with the cabin crew having a quick smoke in the galley every so often. Quite an experience!

 

[Old Timer]

How did you guess - are they in the habit of flying "on fumes"

Well lets put it this way I will never fly with that airline, having friends in the airline industry I have learnt a lot.

 

[WestCoast]

Well lets put it this way I will never fly with that airline, having friends in the airline industry I have learnt a lot.

Interesting. I've flown with Cubana and Onur Air (who've been banned from several European countries in the past!) - I didn't think they were in that league...

 

[notadriver]

By law I thought you had to have 90 minutes of fuel remaining on landing in the tanks unless you were diverted or there was some other emergency (not headwinds)

 

[Butts]

The most "interesting" flight I've ever had was on a Cubana de Aviación Ilyushin Il-96 (a Russian relic all the way from Gatwick to Havana!) with the cabin crew having a quick smoke in the galley every so often. Quite an experience!

Were the passengers allowed a puff as well - I remember well my last cigarette on a plane ......

1998 going to France on a chartered service

Theres nothing worse than getting on a plane wth ashtrays - becoming very rare now- I keep dreaming of the no smoking light going out...I always keep a packet handy in case of doomsday....wonder if any of the 9/11 hijackers allowed the condemned men/women a final snout.

 

[Old Timer]

By law I thought you had to have 90 minutes of fuel remaining on landing in the tanks unless you were diverted or there was some other emergency (not headwinds)

No fuel planning is the responsibility of each individual airline.

The principal being that you have sufficient fuel to circle your destination for a period of time bearing in mind the likelihood of delays at the airport at the estimated arrival time, then the fuel reserve should be sufficient to fly to a defined alternative airport and circle there for a period of time.

For example "on time" at LHX/LGW includes a 20 minute period to be added for a holding pattern in the holding stack, so this would be included in the main fuel.

Each individual airline has its own rules for fuel calculations and I believe that some long haul carriers plan it to the absolute minimum, such that if you were to listen in to say Heathrow ATC during times of extended disruption, you would hear some a/c declaring fuel advisories/emergencies as they literally are at that stage on the limits of their fuel.

I can only comment on KLM's Basic Operations Manual of procedures but this requires any a/c to land with an absolute minimum of 45 mins worth of flying time fuel which is over and above the total fuel requirements calculated. The normal KLM procedure is that the a/c will divert to the pre-defined alternate airport before that situation is realised unless specific authority is given by KLM Movement Control at Schiphol.

If the a/c is detained longer than planned in the holding stock and this will result in the a/c reaching the minimum fuel level +45 mins, the instruction is to issue a "Fuel Advisory" to ATC to indicate the developing situation, with the expectation that ATC will give priority to the a/c. In the event that this cannot be given then an Emergency would be declared.

The Rules for UK airlines are set out in CAA publication CAP 789 "Requirements and Guidance Material for Operators" chapter 13.

Interesting. I've flown with Cubana and Onur Air (who've been banned from several European countries in the past!) - I didn't think they were in that league...

Be well worth following the AF447 saga (the Rio to Paris flight which crashed into the South Atlantic), especially the part about the pitot heads freezing at high altitude being known for several years but AI were unwilling to make the icing issue known globally. AF only changed their European fleet (which did not operate in environments where high altitude icing was an issue) and left their long haul fleet unchanged whereas KLM grounded their entire AI fleet and changed to pitot heads to a US designed and manufactured alternative fitting, which of course did not go down at all well with AI nor with AF as their new "partner airline".

In the years leading up to 2009, there had been a number of incidents involving A3xx series AI a/c pitot heads freezing up with the consequent loss of control when the computers responded to incorrect speed data.

This was known about but nothing was done, thus the pilots on AF447 had absolutely no chance once they flew through the ITCZ and the pitot heads froze.

Other airlines operating through the ITCZ area, such as KLM, will fly around precipitation in there even if it means taking on additional fuel or at worst offloading passengers. I have flown through the edges once because although the pilot (it was a KLM flight) had diverted well away, the precipitation widened out in a very short space of time to where we were and there was insufficient time to deviate further.

Flying through the edges was "interesting" as it was extremely turbulent - at one point we literally dropped several thousand feet instantaneously - so much so that some of the S. Americans on board started praying, and a number of passengrs who were not aware were very frightened. I certainly would not want to fly through the blasted thing as Air France do to save money, I prefer the KLM option of going around even if it does require extra fuel and time.

 

[Old Timer]

For anyone who is interested, here is an actual recording of a KLM 747 declaring a low fuel emergency following a previous landing a/c crashing at Toronto airport.

As they will not be able to land in accordance with the KLM BOM minimum fuel requirements, they request an emergency diversion to Syracuse which will enable them to land with 30 mins worth of fuel, which to KLM is basically empty tanks.

The recording starts with notification to hold by ATC and follows the transmissions to the actual landing at Syracuse in the USA

View attachment KLM Fuel Emergency.mp3

 

[Royston Vasey]

It's now well known that AF's unofficial underfueling (shall we say reduced safety margin) which caused Butts' diverted landing was a contributory factor in the AF447 disaster. The pilots had insufficient fuel to divert around the weather system AND reach CDG, and consequently the pilots decided to choose the latter.

As an aside, the jet stream causes actual flying time from LHR to EWR or JFK to be a full hour longer than the return journey. Given the flight from New York TO London is usually a night flight, I'd much rather that was the longer! Driving out of LHR after 2-3 hours sleep is pretty grim!

 

[Butts]

It's now well known that AF's unofficial underfueling (shall we say reduced safety margin) which caused Butts' diverted landing was a contributory factor in the AF447 disaster. The pilots had insufficient fuel to divert around the weather system AND reach CDG, and consequently the pilots decided to choose the latter.

As an aside, the jet stream causes actual flying time from LHR to EWR or JFK to be a full hour longer than the return journey. Given the flight from New York TO London is usually a night flight, I'd much rather that was the longer! Driving out of LHR after 2-3 hours sleep is pretty grim!

If you are driving a car into headwinds you just increase pressure on the accelerator to maintain your speed surely an aircraft can do the same.

 

[GB]

Yes but you have to balance it with safety and passenger comfort. Large headwinds and tailwinds can cause turbulence which can have a negative affect on the aircraft and its occupants.

 

[Old Timer]

If you are driving a car into headwinds you just increase pressure on the accelerator to maintain your speed surely an aircraft can do the same.

I think the point you are missing here is that the more power you need to face a headwind, the more fuel you will burn if yoy want to maintain airspeed. This should be a basic part of the normal fuel calculation, and an a/c should never find itself meeting an unpredicted headwind.

The alternative is to slow down but then the duration will become extended, and you need more fuel for the additional flying time.

 

[Butts]

I think the point you are missing here is that the more power you need to face a headwind, the more fuel you will burn if yoy want to maintain airspeed. This should be a basic part of the normal fuel calculation, and an a/c should never find itself meeting an unpredicted headwind.

The alternative is to slow down but then the duration will become extended, and you need more fuel for the additional flying time.

Thanks I'm glad driving a car is not so complicated

How do Trains and Ships cope with headwinds ?

 

[Old Timer]

It's now well known that AF's unofficial underfueling (shall we say reduced safety margin) which caused Butts' diverted landing was a contributory factor in the AF447 disaster. The pilots had insufficient fuel to divert around the weather system AND reach CDG, and consequently the pilots decided to choose the latter.

As an aside, the jet stream causes actual flying time from LHR to EWR or JFK to be a full hour longer than the return journey. Given the flight from New York TO London is usually a night flight, I'd much rather that was the longer! Driving out of LHR after 2-3 hours sleep is pretty grim!

I am told that it was the practice to redeclare the destination as Marseiiles, as under Brazillian ATC rules they could not take off for CDG as they did not have suffuicient fuel to meet those rules. Once clear of Brazillian ATC from mid-Atlantic they would declare a diversion back to CDG to the Dakkar ATC who of course have no reason to question that for an a/c in overflight transit.

Personally I wil fly with an airline who I know will tank enough fuel to cover all eventualities and not operate on the basis of in flight diversion to the original destination when the fuel calculations come right.

The way some of these operators are now going forward there will come a time when some poor sod is flying on fumes in the glide path and doesn't make it.

 

[Peter Mugridge]

How do Trains and Ships cope with headwinds ?

Try driving one of these... http://www.hover-gen.com/photograph-galleries/griffon-8000-gallery/ You need to really think about planning a turn in any wind and crosswinds are, shall we say, really going to excercise the brain - especially if there is limited room to maneouvre.

By the way, when that picture of me was taken we were doing 50 knots in the Solent.

 

[Old Timer]

Thanks I'm glad driving a car is not so complicated

How do Trains and Ships cope with headwinds ?

It is a completely different fuel scenario.

Every gallon of avgas costs a lot of money, and the more you carry the more it costs and indeed you have to carry more just to cover the weight of the fuel you are going to have left over, if you understand what I mean.

Excess Avgas sitting in the tanks represents money with no return, therefore some airlines who are struggling financially will pressurise pilots to operate with the absolute minimum, in other words, there is enough to stack in the hold for the normal stack time and that is it. At some point during the holding pattern the pilot has to either (a) divert to another airport - not taken very well by the Operator, or (b) declare a fuel emergency - a reportable occurrence that will potentially end up with the f/deck crew having tea and biscuits with the appropriate Regulatory Authority officials.

The issue for the pilot is whether to stay in the stack and hope he gets down or diverts. If he elects to stay in the stack and then for example something happend and he has to make a go around, he may well find he is out of fuel with no diversion. When there was a security scare at Heathrow a while back, there were a whole series of a/c reporting low fuel emergencies once they were told to hold pattern in the stack, simply because they were on minimum in the stack and could not divert.

As I made out in my post above, I prefer an airline which requires at least 30 mins worth of fuel in the tank following an alternate diversion - eg acts as per the KLM clip rather than hanging on in anticipation.

 

[Butts]

It is a completely different fuel scenario.

Every gallon of avgas costs a lot of money, and the more you carry the more it costs and indeed you have to carry more just to cover the weight of the fuel you are going to have left over, if you understand what I mean.

Excess Avgas sitting in the tanks represents money with no return, therefore some airlines who are struggling financially will pressurise pilots to operate with the absolute minimum, in other words, there is enough to stack in the hold for the normal stack time and that is it. At some point during the holding pattern the pilot has to either (a) divert to another airport - not taken very well by the Operator, or (b) declare a fuel emergency - a reportable occurrence that will potentially end up with the f/deck crew having tea and biscuits with the appropriate Regulatory Authority officials.

The issue for the pilot is whether to stay in the stack and hope he gets down or diverts. If he elects to stay in the stack and then for example something happend and he has to make a go around, he may well find he is out of fuel with no diversion. When there was a security scare at Heathrow a while back, there were a whole series of a/c reporting low fuel emergencies once they were told to hold pattern in the stack, simply because they were on minimum in the stack and could not divert.

As I made out in my post above, I prefer an airline which requires at least 30 mins worth of fuel in the tank following an alternate diversion - eg acts as per the KLM clip rather than hanging on in anticipation.

I thought there was no tax on Av Gas - how can it be so expensive ?

 

[Peter Mugridge]

I thought there was no tax on Av Gas - how can it be so expensive ?

Sheer quantities required, combined with the quantity required to lift any extra weight.

Back in the 1980s when fuel was very cheap compared to today, one airline - I forget which - calculated that every extra 1kg on a Boeing 747 would cost £200 a year in extra fuel consumption.

This is why an increasing number of airlines use bare metal finishes as part of their livery.

 

[Butts]

Sheer quantities required, combined with the quantity required to lift any extra weight.

Back in the 1980s when fuel was very cheap compared to today, one airline - I forget which - calculated that every extra 1kg on a Boeing 747 would cost £200 a year in extra fuel consumption.

This is why an increasing number of airlines use bare metal finishes as part of their livery.

Any idea how much the cost of fuel for a trip across the pond would be ?

 

[Peter Mugridge]

No, but it should be possible to work it out. The quantity of fuel various types use is easily Googled ( usually quoted in tonnes ) and it shouldn't be too difficult to find the price of the stuff. A bit of maths should give the approximate resulting answer.

 

[Butts]

No, but it should be possible to work it out. The quantity of fuel various types use is easily Googled ( usually quoted in tonnes ) and it shouldn't be too difficult to find the price of the stuff. A bit of maths should give the approximate resulting answer.

True, But at this time of night I'm too idle

Just I have never seen a figure in articles about air travel breaking down the actual cost of a trip with fuel,wages,etc and how much they need to break even. Come to think of it have never seen the figures for a train either!!